import type { SceneNode, Choice, EngineEvent } from '../types'
import { SceneManager } from './SceneManager'
import { VideoManager } from './VideoManager'
import { StateManager } from './StateManager'
import { ChoiceSystem } from '../systems/ChoiceSystem'

type EventHandler = (...args: any[]) => void

export class Engine {
  sceneManager: SceneManager
  videoManager: VideoManager
  stateManager: StateManager
  choiceSystem: ChoiceSystem

  private currentScene: SceneNode | null = null
  private events: Map<EngineEvent, Set<EventHandler>> = new Map()
  private ended = false
  private isInitialScene = true

  constructor() {
    this.sceneManager = new SceneManager()
    this.videoManager = new VideoManager()
    this.stateManager = new StateManager()
    this.choiceSystem = new ChoiceSystem()
  }

  on(event: EngineEvent, handler: EventHandler) {
    if (!this.events.has(event)) this.events.set(event, new Set())
    this.events.get(event)!.add(handler)
  }

  off(event: EngineEvent, handler: EventHandler) {
    this.events.get(event)?.delete(handler)
  }

  private emit(event: EngineEvent, ...args: any[]) {
    this.events.get(event)?.forEach((h) => h(...args))
  }

  start() {
    this.ended = false
    this.isInitialScene = true
    const startScene = this.sceneManager.getStartScene()
    this.goToScene(startScene)
  }

  private goToScene(scene: SceneNode) {
    this.currentScene = scene

    if (scene.onEnter) {
      this.stateManager.apply(scene.onEnter)
    }

    const preloadUrls = this.sceneManager.getCandidateUrls(
      scene,
      (conds) => conds ? this.stateManager.evaluate(conds) : true
    )

    this.videoManager.onEnd(() => {
      this.emit('videoEnd', scene)
      this.onVideoEnd(scene)
    })

    if (this.isInitialScene) {
      this.isInitialScene = false
      this.videoManager.playInitial(scene.videoUrl, preloadUrls)
    } else {
      this.videoManager.switchTo(scene.videoUrl, preloadUrls)
    }

    this.emit('sceneChange', scene)
  }

  private onVideoEnd(scene: SceneNode) {
    const validChoices = this.getValidChoices(scene)

    if (validChoices.length > 0) {
      this.emit('choiceRequest', validChoices)

      this.choiceSystem.start(
        validChoices,
        (timerState) => {
          this.emit('choiceTimer', timerState)
        },
        (defaultChoice) => {
          this.emit('choiceTimeout', defaultChoice)
          this.makeChoice(defaultChoice)
        }
      )
    } else if (scene.nextScene) {
      const next = this.sceneManager.getScene(scene.nextScene)
      if (next) {
        this.goToScene(next)
      } else {
        this.endGame()
      }
    } else {
      this.endGame()
    }
  }

  getValidChoices(scene: SceneNode): Choice[] {
    if (!scene.choices) return []
    return scene.choices.filter((c) =>
      !c.conditions || this.stateManager.evaluate(c.conditions)
    )
  }

  makeChoice(choice: Choice) {
    if (!this.currentScene) return

    if (choice.effects) {
      this.stateManager.apply(choice.effects)
    }

    this.stateManager.recordChoice({
      sceneId: this.currentScene.id,
      choiceIndex: this.currentScene.choices?.indexOf(choice) ?? -1,
      choiceText: choice.text,
    })

    const next = this.sceneManager.getScene(choice.targetScene)
    if (next) {
      this.goToScene(next)
    } else {
      this.endGame()
    }
  }

  endGame() {
    this.ended = true
    this.emit('gameEnd')
  }

  resumeScene(sceneId: string, savedState: { variables: Record<string, number>; flags: string[]; history: any[] }) {
    this.stateManager.variables = { ...savedState.variables }
    this.stateManager.flags = new Set(savedState.flags)
    this.stateManager.history = [...savedState.history]

    const scene = this.sceneManager.getScene(sceneId)
    if (!scene) {
      this.endGame()
      return
    }

    this.ended = false
    this.isInitialScene = false

    const preloadUrls = this.sceneManager.getCandidateUrls(
      scene,
      (conds) => conds ? this.stateManager.evaluate(conds) : true
    )

    this.videoManager.switchTo(scene.videoUrl, preloadUrls)

    this.videoManager.onEnd(() => {
      this.emit('videoEnd', scene)
      this.onVideoEnd(scene)
    })

    this.currentScene = scene
    this.emit('sceneChange', scene)
  }

  destroy() {
    this.videoManager.detach()
    this.events.clear()
  }
}